Phenolic compound contents in edible parts of broccoli inflorescences after domestic cooking
Abstract
Total flavonoid and individual hydroxycinnamoyl derivative (sinapic and caffeoyl-quinic acid derivative) contents were evaluated in the edible portions of freshly harvested broccoli (cv Marathon inflorescences) before and after cooking and in the cooking water. High-pressure boiling, low-pressure boiling (conventional), steaming and microwaving were the four domestic cooking processes used in this work. The predominant sinapic acid derivatives were identified as 1,2,2′-trisinapoylgentiobiose and 1,2′-disinapoyl-2-feruloylgentiobiose. In addition 1,2-diferuloylgentiobiose and 1-sinapoyl-2,2′-diferuloylgentiobiose were also identified in broccoli inflorescences. The results showed large differences among the four treatments in their influence on flavonoid and hydroxycinnamoyl derivative contents in broccoli. Clear disadvantages were detected when broccoli was microwaved, namely high losses of flavonoids (97%), sinapic acid derivatives (74%) and caffeoyl-quinic acid derivatives (87%). Conventional boiling led to a significant loss of flavonoids (66%) from fresh raw broccoli, while high-pressure boiling caused considerable leaching (47%) of caffeoyl-quinic acid derivatives into the cooking water. On the other hand, steaming had minimal effects, in terms of loss, on both flavonoid and hydroxycinnamoyl derivative contents. Therefore we can conclude that a greater quantity of phenolic compounds will be provided by consumption of steamed broccoli as compared with broccoli prepared by other cooking processes.
